It actually really matters how you mount heatsinks. Basically it is difficult to say it for a Zipang CPU Cooler, but there is a recommended position as far as I know.
1. The http://img43.imageshack.us/img43/9027/42zpinpb.th.jpg should be the better mounting method.
2. The thing is, that the U-Shape heatpipes should face up towards the sky/universe with the tips. Zipang though has them face 2 different directions, so mounting it like shown in firts picture should probbaly be best for Zipang.